Code

<script language="JavaScript">
${esc.h}${esc.h}${esc.d}content is your content object, and myJSONString is the field that stores the JSON string
var obj = jQuery.parseJSON('${esc.d}content.myJSONString');
${esc.h}${esc.h}You can get the values from the resulting Javascript object.
${esc.h}${esc.h}This example assumes the JSON string has a name value like this: {"name":"John"}
alert(obj.name);
</script>